1. Field of the Invention
This invention relates generally to rolling mills, and is concerned in particular with an improved roll assembly of the "overhung" type, where ring shaped work rolls are mounted on the ends of driven roll shafts.
2. Description of the Prior Art
In the typical overhung roll assembly, a ring shaped roll has a cylindrical bore received on a tapered section of a driven roll supporting shaft. A tapered sleeve is inserted in wedged engagement between the tapered roll shaft section and the cylindrical roll bore. In some cases, the wedged engagement of the sleeve serves as the primary means of transmitting torque from the roll shaft to the roll. In other cases, the tapered sleeve mainly serves as a centering device, with torque being transmitted from the roll shaft to the roll by other means, e.g., through keys or other like mechanical interengagements, or by hydraulically loading adjacent components of the roll assembly against the roll flanks to transmit torque by frictional contact.
When the tapered sleeve serves as the primary torque transmitting component, it exerts substantial radial force on the roll. The roll must therefore be radially thickened in order to provide the strength required to withstand the resulting increased hoop stress. The increased thickness of the roll is accommodated by a reduction in the shaft diameter, which disadvantageously reduces shaft rigidity.
Axial loading of the tapered sleeves or other torque transmitting components of conventional roll assemblies is typically achieved by specially designed hydraulically actuated tools. Such tools are expensive and extremely heavy, usually requiring maintenance personnel to employ lift cranes when engaging and disengaging the tools from the roll assemblies. Non-productive mill downtime is thus prolonged because most mill installations only have a limited number of lift cranes available for use by maintenance personnel.
An objective of the present invention is to provide an overhung roll assembly in which the tapered sleeve serves primarily as a centering device, with torque being transmitted from the roll shaft to the roll by other components of the roll assembly in frictional contact with the roll flanks. Roll hoop stresses are thus advantageously reduced, making it possible to achieve a corresponding reduction in roll thickness and a beneficial increase in shaft diameter.
A companion objective of the present invention is the provision of a simple mechanically actuated arrangement for axially loading the torque transmitting roll assembly components acting in frictional contact with the roll flanks. This is accomplished through the use of low cost light weight tools which can be employed by maintenance personnel without resort to auxiliary equipment such as overhead lift cranes.